This invention relates to leak detection methods and systems, and more particularly, to diagnosis of components used for automotive fuel leak detection in a vapor handling system.
In a vapor handling system for an automotive vehicle, fuel vapor that escapes from a fuel tank is stored in a canister. If there is a leak in the fuel tank, the canister, or any other component of the vapor handling system, fuel vapor could exit through the leak to escape into the atmosphere.
During leak detection, vapor handling systems may be sealed to contain the fuel vapor. However, sealingly containing the fuel vapor may be difficult due to the ability of the fuel vapors to escape through small cracks or crevices or joints and seams within the system that become porous over time. The system components may also malfunction, which may lead to an inaccurate leak detection diagnosis. As a result, it is believed that there should be a component diagnosis to provide more accurate measurements of fuel vapor leakage.
The present invention provides a method of diagnosing components used for leak detection in a closed vapor handling system of an automotive vehicle. This method includes providing leak detection components including a pressure switch that moves at a given relative vacuum, a control valve that operates to allow and prevent flow therethrough, and a shut off valve that operates to allow and prevent flow therethrough, running an engine, determining whether the pressure switch is closed, purging a canister, specifying a fail condition if the control valve is inoperative after purging, ascertaining whether the control valve is inoperative in a flow-through condition or inoperative in a non-flow-through condition if a fail condition is specified, specifying a pass condition if the control valve is functioning after purging, determining whether the shut off valve and pressure switch are malfunctioning if a pass condition is specified based on whether the pressure switch is open, and displaying an error if a component is malfunctioning.
The present invention also provides another method of diagnosing components used for leak detection in a closed vapor handling system of an automotive vehicle. This method includes providing leak detection components including a pressure switch that moves at a given relative vacuum, a control valve that operates to allow flow and prevent flow therethrough, and a shut off valve that operates to allow flow and prevent flow therethrough, running an engine, determining whether the pressure switch is closed, purging a canister; specifying a fail condition if the control valve is inoperative after purging, ascertaining whether the control valve is inoperative in a flow-through condition or inoperative in a non-flow-through condition if a fail condition is specified, specifying a pass condition if the control valve is functioning after purging, determining whether the shut off valve and pressure switch are malfunctioning if a pass condition is specified, displaying an error if a component is malfunctioning; and displaying a no error if the components are functioning. If the pressure switch is open before purging, the ascertaining includes operating the shut off valve to prevent flow therethrough, detecting whether the pressure switch is open, indicating the control valve is inoperative in a non-flow-through condition if the pressure switch is open, and indicating the control valve is inoperative in a flow-through condition if the pressure switch is closed. Alternatively, if the pressure switch is closed before purging, the ascertaining includes indicating the control valve is inoperative in a flow-through condition. If the pressure switch is closed before purging, the determining includes stopping the engine, operating the control valve to allow flow therethrough, detecting whether the pressure switch is open, indicating the shut off valve is inoperative in a non-flow-through condition if the pressure switch is open, and indicating the pressure switch is inoperative in a closed position if the pressure switch is closed. Alternatively, if the pressure switch is open before purging, the determining includes detecting whether the pressure switch is open, indicating the shut off valve is inoperative in a non-flow-through condition if the pressure switch is closed, operating the control valve to allow flow therethrough if the pressure switch is open, detecting whether the pressure switch is open after allowing flow through the control valve, indicating the pressure switch is inoperative in an open position if the pressure switch is open after allowing flow through the control valve, operating the shut off valve and the control valve to prevent flow therethrough if the pressure switch is closed after allowing flow through the control valve, detecting whether the pressure switch is open after preventing flow through the shut off valve, indicating at least one of the shut off valve is inoperative in a flow-through condition and a leak condition exists if the pressure switch is open after preventing flow through the shut off valve, operating the shut off valve to allow flow therethrough if the pressure switch is closed after preventing flow through the shut off valve, determining whether the pressure switch is open after allowing flow through the shut off valve, specifying the shut off valve is inoperative in a non-flow-through condition if the pressure switch is closed after allowing flow through the shut off valve, and specifying a no malfunction condition if the pressure switch is open.
The present invention also provides a system for diagnosis of components used for leak detection in an engine. This system includes a pressure switch, a control valve, a shut off valve, and a processor operatively coupled to the pressure sensing element, the control valve, and the shut off valve and receiving pressure signals from the pressure sensing element and sending signals to the control valve and the shut off valve. The processor runs an engine, determines whether the pressure switch is closed, purges a canister, specifies a fail condition if the control valve is inoperative, ascertains whether the control valve is inoperative in a flow-through condition or inoperative in a non-flow-through condition, specifies a pass condition if the control valve is functioning, determines whether the shut off valve and the pressure switch are malfunctioning, and displays an error if at least one of the pressure switch, the shut off valve, and the control valve is malfunctioning.
The present invention further provides another system for diagnosis of components used for leak detection in an engine. This system includes a pressure switch located on a conduit between a fuel tank and a canister, the canister communicating with an engine and an atmosphere, the fuel tank communicating with the engine, a shut off valve located between the canister and the atmosphere, a control valve located between the canister and the engine, and a processor operatively coupled to the pressure sensing element, the control valve, and the shut off valve and receiving pressure signals from the pressure sensing element and sending signals to the control valve and the shut off valve. The processor runs the engine, determines whether the pressure switch is closed, purges a canister, specifies a fail condition if the control valve is inoperative, ascertains whether the control valve is inoperative in a flow-through condition or inoperative in a non-flow-through condition, specifies a pass condition if the control valve is functioning, determines whether the shut off valve and the pressure switch are malfunctioning, displays an error if at least one of the pressure switch, the shut off valve, and the control valve is malfunctioning, operates the control valve and the shut off valve to allow flow and prevent flow therethrough, stops the engine, and displays a no error if the components are functioning.